If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You need to register
before you can post, click the register link to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

nonlinear regression results

Hi,
I have a set of datapoints which i am trying to fit to the function
y = A*log(B+x) + C*x + D*sqrt(x)
and I am trying to use IMSL NonLinearRegression to do so.
An example of the data points i am trying to fit is attached:
The results are
A = 6.470
B = 0.827
C=-0.494
D= 4.009
I tried to compare the results with those generated by another library and those generated by other curve fitting softwares and, while the values of B, C and D agree with those calculated by IMSL NonLinearRegression, the value of A calculated with all other methods is 2.810.
Could anyone explain why am I getting different results?
Thanks in advance
Mauri